The present invention relates to a blast-protective window construction. More particularly, the invention provides improved glazing for such a window, which reduces assembly time, in some embodiments eliminates the use of liquid sealant during assembly on site, and most importantxe2x80x94improves the resistance of the glass panels to separation from the window frame in response to a blast force.
Many types of glazing systems are known. An example of a simple design intended primarily for the framing of mirrors is the panel mounting proposed by Kain in U.S. Pat. No. 4,006,569. A much more complex design intended to cope with various dimensional irregularities, thermal problems and condensation is disclosed by Unger et al in U.S. Pat. No. 5,356,675.
There are advantages in providing a glazing sub-frame, holding the glass panel, which sub-frame can be fast assembled either at the factory or on the building site to a window frame. For example, the window frame can be joined to the building by workmen who may be less than careful before any glass is brought to the building site, and the glass in its sub-frame is made In the factory and added shortly before completion of construction. A design of, this type is proposed by Gebhard in U.S. Pat. No. 4,364,209. He describes a window frame having a J-shaped channel into which is inserted the glazing strip which has a flexible leg locking into the window frame.
Many glazing arrangements require extensive use of a liquid sealant on site.
Older methods required the use of putty. The on-site use of such sealants is preferably to be avoided, due to delays caused by alloying drying time, mess on site and the difficulties of quality control outside the factory.
The above-mentioned designs are unsuitable for, and indeed not intended for windows required to resist high forces.
One application for high-pressure windows is in viewing underwater events. A further application is in viewing hazardous industrial or laboratory operations where there is a danger of an explosion occurring.
For general civilian use blast protective windows ark designed to withstand explosive blast forces to a level usually determined by standards set by governments or local authorities. Security windows are used in buildings which may be subject to terrorist attacks, in bomb shelters, and in recent years have also come into extensive use in residential buildings provided with security rooms. Such rooms are part of the living quarters of a house or flat, and although reinforced to withstand a high degree of blast forces, and sealable against external gases, the general appearance of such rooms is reasonably similar to that of other rooms in the same building.
In residential areas blast protective windows are suspended from a sill frame by hinges and are designed to be openable, and when closed to be sealed against entry of gases, such sealing providing protection also against liquids.
A known weakness of prior art blast protective windows is that under the extreme pressures resulting from an explosive blast the glass is shattered, but the fragments are still retained as one sheet by means of a plastic covering or sandwiched flexible sheet. The glass is then pulled out of the frame, as due to deformation of the broken sheet the outer dimensions of the sheet suffer size reduction. Prior art designs fail to make adequate provision for preventing such extraction of the glass from the window frame. Obviously, when such broken sheet fails to be retained in its frame the sheet itself may cause injury to persons in its vicinity.
It is therefore one of the objects of the present invention to obviate the disadvantages of prior art glazing systems for blast resistant windows and to provide a system which improves resistance to extraction of the glass from the window frame.
It is a further object of the present invention to separate the glazing operation from window frame construction and thus reduce the; need for skilled on-site labor.
The present invention achieves the above objects by providing a multi-layer security glazing unit for resisting actions of force, comprising a pair of spaced-apart glass panels provided with a reinforcing resin material therebetween and sealed together along at least one common edge thereof by an adhesive material within a rigid clamping channel of substantially U-shapes cross-section.
In a preferred embodiment of the present invention there if provided a blast-protective window, comprising:
a) a multi-layer security glazing unit in combination with
b) a window frame joined and sized to receive and surround said glazing unit; said window frame comprising:
(i) a main framework of vertical and horizontal elements extending in a general plane of a substantially vertical orientation;
(ii) an auxiliary backing framework also extending in a general plane of a substantially vertical orientation, said auxiliary backing framework at least partly protruding across the opening defined by said main framework for at least indirectly supporting a first face of said glazing unit, said main framework and said auxiliary framework being integrally joined, and together having a substantially L-shaped cross-section along the surrounding common edge thereof, and
(iii) a clamping element adapted to be attached to said main framework with a surface thereof adjacent to, and at least indirectly supporting a second face of said glazing unit.
In a most preferred embodiment of the present invention there is provided a blast-protective window wherein the auxiliary backing framework and the clamping elements are each provided with a stepped surface. Upon assembly the distance between the interfacing inner surfaces of the backing framework and the clamping element supporting the faces of the glazing unit is less than the distance between the portions of the backing framework and the clamping element adjacent to the rigid clamping channel.
Yet further embodiments of the invention will be described hereinafter.
It will thus be realized that the novel glazing system of the present invention serves to secure the glass sheets to a U channel, which U channel is quite easily retained in the window frame and is firmly restrained from extraction by shoulders or ledges integral to the frame.
Furthermore, the primary glazing operation, involving the use of a liquid sealant filling the rigid U channel and gripping the glass therein, need not be carried out at the construction site but in the factory, where such work can be better controlled and executed. The glass, together with its sub-frame is best transported to the building site just before the building is being completed, and is thus protected from the dangers of ongoing construction activities. The workmen installing the window frame in the building wall can carry out their task without concern for the glass. In some embodiments of the present invention, the window pane with its sub frame may be installed without requiring the use on site of liquid sealants.